body{
    background-color: #dedede5c;
}
div{
    width: 70%;
    margin: 0 auto;
}
.b{
    height: 30px;
    text-align: left;
}
.a{
    height: 200px;
    text-align:left;
    background: #0095ff0d;
    line-height: 20px;
}
table{
    width:70%;
    border-collapse:collapse;/* 取消表格边框 */
    letter-spacing:1px;/* 文字缩进 */
    margin: 0 auto;
}
table,th,tr,td{
    border-bottom:1px solid #dedede;/* 表格横线 */
    padding:14px;
    text-align: center;
}